Performance evaluation of IP-based relay communications for wide-area protection employing external time synchronization

This paper describes the application of IP (Internet protocol)-based communications, now used broadly in a variety of utility applications, to two major types of delay-critical wide-area power system protection in conjunction with time transfer systems. One type of protection is a centralized multi-zone fault clearing protection with a current differential scheme, providing integrated primary and backup protection functions for better selectivity, smaller outage areas and faster operation times than conventional distance backup protection, The other is a system-wide stabilizing protection for preventing out-of-step. Transmission requirements are presented for each type of protection, and IP-based communications examined with respect to delays.